The aim of this study was to examine the influence of different small-sided games (SSGs) format on external, internal load and technical actions of professional U-23 portuguese soccer players. Eight players (20.1±0.8 years, 180.4±7.2 cm, 75.9±4.9 kg) performed three different 4 vs. 4 ball possession SSGs (3x3 min play/rest) in different pitch dimensions, SSG1 16x24 m, SSG2 20x30 m and SSG3 24x36 m. All SSGs were video recorded for technical actions analysis. WIMU PROTM (RealTrack Systems, Almeria, Spain) inertial devices were used for internal and external load data collection. The distribution normality was determined with the Shapiro-Wilk test. Parametric and nonparametric statistics were selected accordingly. Statistical Package for the Social Sciences (SPSS™ 25.0 version) was used for data analysis. No significant differences were observed comparing the different SSGs in total distance covered, acceleration/deceleration distance, as well as in maximal and mean heart rate. Regarding the technical actions, no significant differences were observed in successful passes, contrary to the observed from SSG1 to SSG3 in duels (7.00±2.13; 4.38±2.44; 4.25±1.98), number of balls lost (2.63±1.30; 1.00±0.53; 0.88±1.12) and in between SSGs in high-speed running (p<0.05, ES=0.37). In senior and professional soccer players, the modification of the pitch size between 16x24 m and 24x36 m during 4 vs. 4 ball possession SSGs with 3x3 min play/rest promotes modifications in the dynamic of technical actions and internal and external training load variables Keywords: Small-sided games, Professional soccer, Technical actions, External and internal load, Performance.